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To:     Lina Iyer <ilina@codeaurora.org>
From:   Stephen Boyd <swboyd@chromium.org>
In-Reply-To: <20180409153631.GB19682@codeaurora.org>
Cc:     andy.gross@linaro.org, david.brown@linaro.org,
        linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org,
        rnayak@codeaurora.org, bjorn.andersson@linaro.org,
        linux-kernel@vger.kernel.org, evgreen@chromium.org,
        dianders@chromium.org
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 <20180409153631.GB19682@codeaurora.org>
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Subject: Re: [PATCH v5 04/10] drivers: qcom: rpmh: add RPMH helper functions
Date:   Tue, 10 Apr 2018 19:23:08 -0700
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Quoting Lina Iyer (2018-04-09 08:36:31)
> On Fri, Apr 06 2018 at 19:21 -0600, Stephen Boyd wrote:
> >Quoting Lina Iyer (2018-04-05 09:18:28)
> >> diff --git a/include/soc/qcom/rpmh.h b/include/soc/qcom/rpmh.h
> >> new file mode 100644
> >> index 000000000000..95334d4c1ede
> >> --- /dev/null
> >> +++ b/include/soc/qcom/rpmh.h
> >> @@ -0,0 +1,34 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +/*
> >> + * Copyright (c) 2016-2018, The Linux Foundation. All rights reserved.
> >> + */
> >> +
> >> +#ifndef __SOC_QCOM_RPMH_H__
> >> +#define __SOC_QCOM_RPMH_H__
> >> +
> >> +#include <soc/qcom/tcs.h>
> >> +#include <linux/platform_device.h>
> >> +
> >> +struct rpmh_client;
> >> +
> >> +#if IS_ENABLED(CONFIG_QCOM_RPMH)
> >> +int rpmh_write(struct rpmh_client *rc, enum rpmh_state state,
> >> +              const struct tcs_cmd *cmd, u32 n);
> >> +
> >> +struct rpmh_client *rpmh_get_client(struct platform_device *pdev);
> >> +
> >> +void rpmh_release(struct rpmh_client *rc);
> >
> >Please get rid of this 'client' layer and fold it into the rpmh driver.
> >Everything that uses the rpmh_client is a child device of the rpmh
> >device so they should be able to just pass in their device pointer as
> >their 'handle' and have the rpmh driver take that, get the parent device
> >pointer, and pull an rpmh_drv structure out of there. The 'common' code
> >can go into the base rpmh driver and get used from there and then we
> >don't have to hop between two files to see how rpmh is used by the
> >consumers. Code complexity goes down this way.
> =

> That would be not be a good idea. This layer is not just providing an
> API interface. There is resource buffering, handling of memory for
> requests and downstream quirks and debug going on in this layer. It
> would be unwise to clobber the hardware centric rpmh-rsc layer. If you
> look at the series as a whole, you would understand why this is
> necessary. I plan to build more on top of these patches in the future as
> we add support for system low power modes. The complexity doesn't go
> away, it just thrown in to another file, which is already decently
> sized.
> =

> I could try to use the device as a handle, and internally work on
> getting the drv and other information from it, if that helps. But I do
> not want to clobber these two files together. It doesn't help
> maintainability.

Using the device as a handle is a good start. Let's see how it looks
once that part of the code gets replaced. I still fail to see how buffer
management and requests are any different from poking the hardware, but
OK. Maybe if this was a TCS "library" on top of the rpmh hardware
interface?